Adducts of epoxy resins, such as, for example, the diethylenetriamine adduct with the diglycidyl ether of bisphenol A, are known, for example, from page 7-16 of the Handbook of Epoxy Resins, by Henry Lee and Kris Neville, published by McGraw-Hill, Inc. (1967). These adducts find use as lower volatility, higher viscosity and modified reactivity curing agents for epoxy resins, relative to the free (unadducted) polyamine, per se. Daniel A. Scola in Developments in Reinforced Plastics-4 published by Elsevier Applied Science Publishers Ltd., England, pages 196-206 (1984) describes amine adducts of epoxy resins wherein the epoxy resin was selected from the diglycidyl ether of bisphenol A, tetraglycidyl 4,4'-diaminodiphenylmethane, triglycidyl p-aminophenol, epoxy phenol or cresol novalacs, hydrogenated diglycidyl ether of bisphenol A and combinations thereof and the amine was selected from the aliphatic, cycloaliphatic, aromatic and alkylaromatic diamines. Polymercaptan adducts of epoxy resins are also described, wherein the epoxy resin was selected from the diglycidyl ether of bisphenol A, an epoxy novalac blend, or a blend of the diglycidyl ether of bisphenol A with p-tertiary-butylphenolglycidyl ether and the polymercaptan was selected from 2,2'-dimercaptodiethyl ether, 1,2-dimercaptopropane, 1,3-dimercaptopropanol-2 and bis(2-mercaptoethylsulphide). Certain of the epoxy resin adducts provided cured epoxy resins with improvements in one or more physical and mechanical properties, such as, for example, tensile strength, tensile elongation, flexural strength, impact strength, moisture resistance and chemical resistance, relative to the free (unadducted) polyamine or polymercaptan per se. J. Klee, et al. in Crosslinked Epoxies published by Walter de Gruyter and Co., Berlin, pages 47-54 (1987) describes the synthesis and analytical characterization of adducts of the diglycidyl ether of bisphenol A with primary monoamines including aniline, p-chloroaniline, benzylamine and cyclohexylamine. None of the aforementioned epoxy resin adducts or the epoxy resins cured with said adducts contain mesogenic or rodlike moieties.
The present invention provides adducts of epoxy resins containing one or more mesogenic or rodlike moieties. These adducts provide cured epoxy resins with improvements in many physical and mechanical properties, including, for example, tensile and flexural modulus, glass transition temperature, tensile strength and elongation, flexural strength and chemical resistance, relative to epoxy resins cured with epoxy resin adducts free of mesogenic or rodlike moieties. Incorporation of one or more mesogenic or rodlike structures into the curable epoxy resin formulation via the use of the adducts containing one or more mesogenic or rodlike moieties of the present invention can provide a susceptibility for molecular level orientation leading to a ordering of the thermoset thereof.